1 files changed, 70 insertions, 0 deletions
diff --git a/tex/context/base/l-set.lua b/tex/context/base/l-set.lua
new file mode 100644
index 000000000..2bcf664f8
--- /dev/null
+++ b/tex/context/base/l-set.lua
@@ -0,0 +1,70 @@
+-- filename : l-set.lua
+-- author   : Hans Hagen, PRAGMA-ADE, Hasselt NL
+-- copyright: PRAGMA ADE / ConTeXt Development Team
+-- license  : see context related readme files
+
+if not versions then versions = { } end versions['l-set'] = 1.001
+
+if not set then set = { } end
+
+do
+
+    local nums   = { }
+    local tabs   = { }
+    local concat = table.concat
+
+    set.create = table.tohash
+
+    function set.tonumber(t)
+        if next(t) then
+            local s = ""
+        --  we could save mem by sorting, but it slows down
+            for k, v in pairs(t) do
+                if v then
+                --  why bother about the leading space
+                    s = s .. " " .. k
+                end
+            end
+            if not nums[s] then
+                tabs[#tabs+1] = t
+                nums[s] = #tabs
+            end
+            return nums[s]
+        else
+            return 0
+        end
+    end
+
+    function set.totable(n)
+        if n == 0 then
+            return { }
+        else
+            return tabs[n] or { }
+        end
+    end
+
+    function set.contains(n,s)
+        if type(n) == "table" then
+            return n[s]
+        elseif n == 0 then
+            return false
+        else
+            local t = tabs[n]
+            return t and t[s]
+        end
+    end
+
+end
+
+--~ local c = set.create{'aap','noot','mies'}
+--~ local s = set.tonumber(c)
+--~ local t = set.totable(s)
+--~ print(t['aap'])
+--~ local c = set.create{'zus','wim','jet'}
+--~ local s = set.tonumber(c)
+--~ local t = set.totable(s)
+--~ print(t['aap'])
+--~ print(t['jet'])
+--~ print(set.contains(t,'jet'))
+--~ print(set.contains(t,'aap'))
+